\begin{code}
module Type (
- -- re-exports from TypeRep:
- Type,
- Kind, TyVarSubst,
-
- superKind, superBoxity, -- KX and BX respectively
- liftedBoxity, unliftedBoxity, -- :: BX
- openKindCon, -- :: KX
- typeCon, -- :: BX -> KX
- liftedTypeKind, unliftedTypeKind, openTypeKind, -- :: KX
- mkArrowKind, mkArrowKinds, -- :: KX -> KX -> KX
-
+ -- re-exports from TypeRep
+ TyThing(..), Type, PredType(..), ThetaType,
funTyCon,
- usageKindCon, -- :: KX
- usageTypeKind, -- :: KX
- usOnceTyCon, usManyTyCon, -- :: $
- usOnce, usMany, -- :: $
+ -- Re-exports from Kind
+ module Kind,
- -- exports from this module:
- hasMoreBoxityInfo, defaultKind,
+ -- Re-exports from TyCon
+ PrimRep(..),
mkTyVarTy, mkTyVarTys, getTyVar, getTyVar_maybe, isTyVarTy,
mkAppTy, mkAppTys, splitAppTy, splitAppTys, splitAppTy_maybe,
- mkFunTy, mkFunTys, splitFunTy, splitFunTy_maybe, splitFunTys, splitFunTysN,
- funResultTy, funArgTy, zipFunTys,
+ mkFunTy, mkFunTys, splitFunTy, splitFunTy_maybe,
+ splitFunTys, splitFunTysN,
+ funResultTy, funArgTy, zipFunTys, isFunTy,
- mkTyConApp, mkTyConTy,
+ mkGenTyConApp, mkTyConApp, mkTyConTy,
tyConAppTyCon, tyConAppArgs,
splitTyConApp_maybe, splitTyConApp,
- splitAlgTyConApp_maybe, splitAlgTyConApp,
-
- mkUTy, splitUTy, splitUTy_maybe,
- isUTy, uaUTy, unUTy, liftUTy, mkUTyM,
- isUsageKind, isUsage, isUTyVar,
- mkSynTy, deNoteType,
+ mkSynTy,
- repType, splitRepFunTys, splitNewType_maybe, typePrimRep,
+ repType, typePrimRep, coreView, deepCoreView,
mkForAllTy, mkForAllTys, splitForAllTy_maybe, splitForAllTys,
- applyTy, applyTys, hoistForAllTys, isForAllTy,
+ applyTy, applyTys, isForAllTy, dropForAlls,
- -- Predicates and the like
- PredType(..), getClassPredTys_maybe, getClassPredTys,
- isClassPred, isTyVarClassPred,
- mkDictTy, mkPredTy, mkPredTys, splitPredTy_maybe, predTyUnique,
- splitDictTy, splitDictTy_maybe, isDictTy, predRepTy, splitDFunTy,
- mkClassPred, predMentionsIPs, inheritablePred, isIPPred, mkPredName,
+ -- Source types
+ predTypeRep, mkPredTy, mkPredTys,
- -- Tau, Rho, Sigma
- TauType, RhoType, SigmaType, ThetaType,
- isTauTy, mkRhoTy, splitRhoTy, splitMethodTy,
- mkSigmaTy, isSigmaTy, splitSigmaTy,
- getDFunTyKey,
+ -- Newtypes
+ splitRecNewType_maybe,
-- Lifting and boxity
- isUnLiftedType, isUnboxedTupleType, isAlgType, isDataType, isNewType,
+ isUnLiftedType, isUnboxedTupleType, isAlgType, isPrimitiveType,
+ isStrictType, isStrictPred,
-- Free variables
tyVarsOfType, tyVarsOfTypes, tyVarsOfPred, tyVarsOfTheta,
- namesOfType, usageAnnOfType, typeKind, addFreeTyVars,
+ typeKind, addFreeTyVars,
-- Tidying up for printing
- tidyType, tidyTypes,
- tidyOpenType, tidyOpenTypes,
- tidyTyVar, tidyTyVars, tidyFreeTyVars,
- tidyTopType, tidyPred,
+ tidyType, tidyTypes,
+ tidyOpenType, tidyOpenTypes,
+ tidyTyVarBndr, tidyFreeTyVars,
+ tidyOpenTyVar, tidyOpenTyVars,
+ tidyTopType, tidyPred,
- -- Seq
- seqType, seqTypes
+ -- Comparison
+ coreEqType, tcEqType, tcEqTypes, tcCmpType, tcCmpTypes,
+ tcEqPred, tcCmpPred, tcEqTypeX,
+ -- Seq
+ seqType, seqTypes,
+
+ -- Type substitutions
+ TvSubst(..), -- Representation visible to a few friends
+ TvSubstEnv, emptyTvSubst,
+ mkTvSubst, zipTvSubst, zipTopTvSubst, mkTopTvSubst,
+ getTvSubstEnv, setTvSubstEnv, getTvInScope, extendTvInScope,
+ extendTvSubst, extendTvSubstList, isInScope,
+
+ -- Performing substitution on types
+ substTy, substTys, substTyWith, substTheta, substTyVar,
+ deShadowTy,
+
+ -- Pretty-printing
+ pprType, pprParendType, pprTyThingCategory,
+ pprPred, pprTheta, pprThetaArrow, pprClassPred
) where
#include "HsVersions.h"
import TypeRep
--- Other imports:
-
-import {-# SOURCE #-} DataCon( DataCon )
-import {-# SOURCE #-} PprType( pprType ) -- Only called in debug messages
-import {-# SOURCE #-} Subst ( mkTyVarSubst, substTy )
-
-- friends:
+import Kind
import Var ( Var, TyVar, tyVarKind, tyVarName, setTyVarName )
import VarEnv
import VarSet
-import OccName ( mkDictOcc )
-import Name ( Name, NamedThing(..), OccName, mkLocalName, tidyOccName )
-import NameSet
-import Class ( classTyCon, Class )
-import TyCon ( TyCon,
+import Name ( NamedThing(..), mkInternalName, tidyOccName )
+import Class ( Class, classTyCon )
+import TyCon ( TyCon, isRecursiveTyCon, isPrimTyCon,
isUnboxedTupleTyCon, isUnLiftedTyCon,
- isFunTyCon, isDataTyCon, isNewTyCon, newTyConRep,
- isAlgTyCon, isSynTyCon, tyConArity,
- tyConKind, tyConDataCons, getSynTyConDefn,
- tyConPrimRep
+ isFunTyCon, isNewTyCon, newTyConRep, newTyConRhs,
+ isAlgTyCon, isSynTyCon, tyConArity, newTyConRhs_maybe,
+ tyConKind, getSynTyConDefn, PrimRep(..), tyConPrimRep,
)
-- others
-import Maybes ( maybeToBool )
-import SrcLoc ( SrcLoc, noSrcLoc )
-import PrimRep ( PrimRep(..) )
-import Unique ( Unique, Uniquable(..) )
-import Util ( mapAccumL, seqList, thenCmp )
+import CmdLineOpts ( opt_DictsStrict )
+import SrcLoc ( noSrcLoc )
+import Unique ( Uniquable(..) )
+import Util ( mapAccumL, seqList, lengthIs, snocView, thenCmp, isEqual )
import Outputable
import UniqSet ( sizeUniqSet ) -- Should come via VarSet
+import Maybe ( isJust )
\end{code}
%************************************************************************
%* *
-\subsection{Stuff to do with kinds.}
+ Type representation
%* *
%************************************************************************
+In Core, we "look through" non-recursive newtypes and PredTypes.
+
\begin{code}
-hasMoreBoxityInfo :: Kind -> Kind -> Bool
-hasMoreBoxityInfo k1 k2
- | k2 == openTypeKind = True
- | otherwise = k1 == k2
-
-defaultKind :: Kind -> Kind
--- Used when generalising: default kind '?' to '*'
-defaultKind kind | kind == openTypeKind = liftedTypeKind
- | otherwise = kind
+{-# INLINE coreView #-}
+coreView :: Type -> Maybe Type
+-- Srips off the *top layer only* of a type to give
+-- its underlying representation type.
+-- Returns Nothing if there is nothing to look through.
+--
+-- By being non-recursive and inlined, this case analysis gets efficiently
+-- joined onto the case analysis that the caller is already doing
+coreView (NoteTy _ ty) = Just ty
+coreView (PredTy p) = Just (predTypeRep p)
+coreView (TyConApp tc tys) = expandNewTcApp tc tys
+coreView ty = Nothing
+
+deepCoreView :: Type -> Type
+-- Apply coreView recursively
+deepCoreView ty
+ | Just ty' <- coreView ty = deepCoreView ty'
+deepCoreView (TyVarTy tv) = TyVarTy tv
+deepCoreView (TyConApp tc tys) = TyConApp tc (map deepCoreView tys)
+deepCoreView (AppTy t1 t2) = AppTy (deepCoreView t1) (deepCoreView t2)
+deepCoreView (FunTy t1 t2) = FunTy (deepCoreView t1) (deepCoreView t2)
+deepCoreView (ForAllTy tv ty) = ForAllTy tv (deepCoreView ty)
+ -- No NoteTy, no PredTy
+
+expandNewTcApp :: TyCon -> [Type] -> Maybe Type
+-- A local helper function (not exported)
+-- Expands *the outermoset level of* a newtype application to
+-- *either* a vanilla TyConApp (recursive newtype, or non-saturated)
+-- *or* the newtype representation (otherwise), meaning the
+-- type written in the RHS of the newtype decl,
+-- which may itself be a newtype
+--
+-- Example: newtype R = MkR S
+-- newtype S = MkS T
+-- newtype T = MkT (T -> T)
+-- expandNewTcApp on R gives Just S
+-- on S gives Just T
+-- on T gives Nothing (no expansion)
+
+expandNewTcApp tc tys = case newTyConRhs_maybe tc tys of
+ Nothing -> Nothing
+ Just (tenv, rhs) -> Just (substTy (mkTopTvSubst tenv) rhs)
\end{code}
mkTyVarTys = map mkTyVarTy -- a common use of mkTyVarTy
getTyVar :: String -> Type -> TyVar
-getTyVar msg (TyVarTy tv) = tv
-getTyVar msg (PredTy p) = getTyVar msg (predRepTy p)
-getTyVar msg (NoteTy _ t) = getTyVar msg t
-getTyVar msg ty@(UsageTy _ _) = pprPanic "getTyVar: UTy:" (text msg $$ pprType ty)
-getTyVar msg other = panic ("getTyVar: " ++ msg)
-
-getTyVar_maybe :: Type -> Maybe TyVar
-getTyVar_maybe (TyVarTy tv) = Just tv
-getTyVar_maybe (NoteTy _ t) = getTyVar_maybe t
-getTyVar_maybe (PredTy p) = getTyVar_maybe (predRepTy p)
-getTyVar_maybe ty@(UsageTy _ _) = pprPanic "getTyVar_maybe: UTy:" (pprType ty)
-getTyVar_maybe other = Nothing
+getTyVar msg ty = case getTyVar_maybe ty of
+ Just tv -> tv
+ Nothing -> panic ("getTyVar: " ++ msg)
isTyVarTy :: Type -> Bool
-isTyVarTy (TyVarTy tv) = True
-isTyVarTy (NoteTy _ ty) = isTyVarTy ty
-isTyVarTy (PredTy p) = isTyVarTy (predRepTy p)
-isTyVarTy ty@(UsageTy _ _) = pprPanic "isTyVarTy: UTy:" (pprType ty)
-isTyVarTy other = False
+isTyVarTy ty = isJust (getTyVar_maybe ty)
+
+getTyVar_maybe :: Type -> Maybe TyVar
+getTyVar_maybe ty | Just ty' <- coreView ty = getTyVar_maybe ty'
+getTyVar_maybe (TyVarTy tv) = Just tv
+getTyVar_maybe other = Nothing
\end{code}
\begin{code}
mkAppTy orig_ty1 orig_ty2
- = ASSERT( not (isPredTy orig_ty1) ) -- Predicates are of kind *
- UASSERT2( not (isUTy orig_ty2), pprType orig_ty1 <+> pprType orig_ty2 )
- -- argument must be unannotated
- mk_app orig_ty1
+ = mk_app orig_ty1
where
mk_app (NoteTy _ ty1) = mk_app ty1
- mk_app (TyConApp tc tys) = mkTyConApp tc (tys ++ [orig_ty2])
- mk_app ty@(UsageTy _ _) = pprPanic "mkAppTy: UTy:" (pprType ty)
+ mk_app (TyConApp tc tys) = mkGenTyConApp tc (tys ++ [orig_ty2])
mk_app ty1 = AppTy orig_ty1 orig_ty2
+ -- We call mkGenTyConApp because the TyConApp could be an
+ -- under-saturated type synonym. GHC allows that; e.g.
+ -- type Foo k = k a -> k a
+ -- type Id x = x
+ -- foo :: Foo Id -> Foo Id
+ --
+ -- Here Id is partially applied in the type sig for Foo,
+ -- but once the type synonyms are expanded all is well
mkAppTys :: Type -> [Type] -> Type
mkAppTys orig_ty1 [] = orig_ty1
-- returns to (Ratio Integer), which has needlessly lost
-- the Rational part.
mkAppTys orig_ty1 orig_tys2
- = ASSERT( not (isPredTy orig_ty1) ) -- Predicates are of kind *
- UASSERT2( not (any isUTy orig_tys2), pprType orig_ty1 <+> fsep (map pprType orig_tys2) )
- -- arguments must be unannotated
- mk_app orig_ty1
+ = mk_app orig_ty1
where
mk_app (NoteTy _ ty1) = mk_app ty1
- mk_app (TyConApp tc tys) = mkTyConApp tc (tys ++ orig_tys2)
- mk_app ty@(UsageTy _ _) = pprPanic "mkAppTys: UTy:" (pprType ty)
+ mk_app (TyConApp tc tys) = mkGenTyConApp tc (tys ++ orig_tys2)
+ -- mkGenTyConApp: see notes with mkAppTy
mk_app ty1 = foldl AppTy orig_ty1 orig_tys2
splitAppTy_maybe :: Type -> Maybe (Type, Type)
-splitAppTy_maybe (FunTy ty1 ty2) = Just (TyConApp funTyCon [unUTy ty1], unUTy ty2)
+splitAppTy_maybe ty | Just ty' <- coreView ty = splitAppTy_maybe ty'
+splitAppTy_maybe (FunTy ty1 ty2) = Just (TyConApp funTyCon [ty1], ty2)
splitAppTy_maybe (AppTy ty1 ty2) = Just (ty1, ty2)
-splitAppTy_maybe (NoteTy _ ty) = splitAppTy_maybe ty
-splitAppTy_maybe (PredTy p) = splitAppTy_maybe (predRepTy p)
-splitAppTy_maybe (TyConApp tc []) = Nothing
-splitAppTy_maybe (TyConApp tc tys) = split tys []
- where
- split [ty2] acc = Just (TyConApp tc (reverse acc), ty2)
- split (ty:tys) acc = split tys (ty:acc)
-
-splitAppTy_maybe ty@(UsageTy _ _) = pprPanic "splitAppTy_maybe: UTy:" (pprType ty)
-splitAppTy_maybe other = Nothing
+splitAppTy_maybe (TyConApp tc tys) = case snocView tys of
+ Nothing -> Nothing
+ Just (tys',ty') -> Just (TyConApp tc tys', ty')
+splitAppTy_maybe other = Nothing
splitAppTy :: Type -> (Type, Type)
splitAppTy ty = case splitAppTy_maybe ty of
splitAppTys :: Type -> (Type, [Type])
splitAppTys ty = split ty ty []
where
+ split orig_ty ty args | Just ty' <- coreView ty = split orig_ty ty' args
split orig_ty (AppTy ty arg) args = split ty ty (arg:args)
- split orig_ty (NoteTy _ ty) args = split orig_ty ty args
- split orig_ty (PredTy p) args = split orig_ty (predRepTy p) args
- split orig_ty (FunTy ty1 ty2) args = ASSERT( null args )
- (TyConApp funTyCon [], [unUTy ty1,unUTy ty2])
split orig_ty (TyConApp tc tc_args) args = (TyConApp tc [], tc_args ++ args)
- split orig_ty (UsageTy _ _) args = pprPanic "splitAppTys: UTy:" (pprType orig_ty)
+ split orig_ty (FunTy ty1 ty2) args = ASSERT( null args )
+ (TyConApp funTyCon [], [ty1,ty2])
split orig_ty ty args = (orig_ty, args)
\end{code}
\begin{code}
mkFunTy :: Type -> Type -> Type
-mkFunTy arg res = UASSERT2( isUTy arg && isUTy res, pprType arg <+> pprType res )
- FunTy arg res
+mkFunTy arg res = FunTy arg res
mkFunTys :: [Type] -> Type -> Type
-mkFunTys tys ty = UASSERT2( all isUTy (ty:tys), fsep (map pprType (tys++[ty])) )
- foldr FunTy ty tys
+mkFunTys tys ty = foldr FunTy ty tys
+
+isFunTy :: Type -> Bool
+isFunTy ty = isJust (splitFunTy_maybe ty)
splitFunTy :: Type -> (Type, Type)
-splitFunTy (FunTy arg res) = (arg, res)
-splitFunTy (NoteTy _ ty) = splitFunTy ty
-splitFunTy (PredTy p) = splitFunTy (predRepTy p)
-splitFunTy ty@(UsageTy _ _) = pprPanic "splitFunTy: UTy:" (pprType ty)
+splitFunTy ty | Just ty' <- coreView ty = splitFunTy ty'
+splitFunTy (FunTy arg res) = (arg, res)
+splitFunTy other = pprPanic "splitFunTy" (ppr other)
splitFunTy_maybe :: Type -> Maybe (Type, Type)
-splitFunTy_maybe (FunTy arg res) = Just (arg, res)
-splitFunTy_maybe (NoteTy _ ty) = splitFunTy_maybe ty
-splitFunTy_maybe (PredTy p) = splitFunTy_maybe (predRepTy p)
-splitFunTy_maybe ty@(UsageTy _ _) = pprPanic "splitFunTy_maybe: UTy:" (pprType ty)
-splitFunTy_maybe other = Nothing
+splitFunTy_maybe ty | Just ty' <- coreView ty = splitFunTy_maybe ty'
+splitFunTy_maybe (FunTy arg res) = Just (arg, res)
+splitFunTy_maybe other = Nothing
splitFunTys :: Type -> ([Type], Type)
splitFunTys ty = split [] ty ty
where
- split args orig_ty (FunTy arg res) = split (arg:args) res res
- split args orig_ty (NoteTy _ ty) = split args orig_ty ty
- split args orig_ty (PredTy p) = split args orig_ty (predRepTy p)
- split args orig_ty (UsageTy _ _) = pprPanic "splitFunTys: UTy:" (pprType orig_ty)
- split args orig_ty ty = (reverse args, orig_ty)
-
-splitFunTysN :: String -> Int -> Type -> ([Type], Type)
-splitFunTysN msg orig_n orig_ty = split orig_n [] orig_ty orig_ty
- where
- split 0 args syn_ty ty = (reverse args, syn_ty)
- split n args syn_ty (FunTy arg res) = split (n-1) (arg:args) res res
- split n args syn_ty (NoteTy _ ty) = split n args syn_ty ty
- split n args syn_ty (PredTy p) = split n args syn_ty (predRepTy p)
- split n args syn_ty (UsageTy _ _) = pprPanic "splitFunTysN: UTy:" (pprType orig_ty)
- split n args syn_ty ty = pprPanic ("splitFunTysN: " ++ msg) (int orig_n <+> pprType orig_ty)
+ split args orig_ty ty | Just ty' <- coreView ty = split args orig_ty ty'
+ split args orig_ty (FunTy arg res) = split (arg:args) res res
+ split args orig_ty ty = (reverse args, orig_ty)
+
+splitFunTysN :: Int -> Type -> ([Type], Type)
+-- Split off exactly n arg tys
+splitFunTysN 0 ty = ([], ty)
+splitFunTysN n ty = case splitFunTy ty of { (arg, res) ->
+ case splitFunTysN (n-1) res of { (args, res) ->
+ (arg:args, res) }}
zipFunTys :: Outputable a => [a] -> Type -> ([(a,Type)], Type)
zipFunTys orig_xs orig_ty = split [] orig_xs orig_ty orig_ty
where
- split acc [] nty ty = (reverse acc, nty)
- split acc (x:xs) nty (FunTy arg res) = split ((x,arg):acc) xs res res
- split acc xs nty (NoteTy _ ty) = split acc xs nty ty
- split acc xs nty (PredTy p) = split acc xs nty (predRepTy p)
- split acc xs nty (UsageTy _ _) = pprPanic "zipFunTys: UTy:" (ppr orig_xs <+> pprType orig_ty)
- split acc (x:xs) nty ty = pprPanic "zipFunTys" (ppr orig_xs <+> pprType orig_ty)
+ split acc [] nty ty = (reverse acc, nty)
+ split acc xs nty ty
+ | Just ty' <- coreView ty = split acc xs nty ty'
+ split acc (x:xs) nty (FunTy arg res) = split ((x,arg):acc) xs res res
+ split acc (x:xs) nty ty = pprPanic "zipFunTys" (ppr orig_xs <+> ppr orig_ty)
funResultTy :: Type -> Type
-funResultTy (FunTy arg res) = res
-funResultTy (NoteTy _ ty) = funResultTy ty
-funResultTy (PredTy p) = funResultTy (predRepTy p)
-funResultTy (UsageTy _ ty) = funResultTy ty
-funResultTy ty = pprPanic "funResultTy" (pprType ty)
+funResultTy ty | Just ty' <- coreView ty = funResultTy ty'
+funResultTy (FunTy arg res) = res
+funResultTy ty = pprPanic "funResultTy" (ppr ty)
funArgTy :: Type -> Type
-funArgTy (FunTy arg res) = arg
-funArgTy (NoteTy _ ty) = funArgTy ty
-funArgTy (PredTy p) = funArgTy (predRepTy p)
-funArgTy (UsageTy _ ty) = funArgTy ty
-funArgTy ty = pprPanic "funArgTy" (pprType ty)
+funArgTy ty | Just ty' <- coreView ty = funArgTy ty'
+funArgTy (FunTy arg res) = arg
+funArgTy ty = pprPanic "funArgTy" (ppr ty)
\end{code}
---------------------------------------------------------------------
TyConApp
~~~~~~~~
+@mkTyConApp@ is a key function, because it builds a TyConApp, FunTy or PredTy,
+as apppropriate.
\begin{code}
+mkGenTyConApp :: TyCon -> [Type] -> Type
+mkGenTyConApp tc tys
+ | isSynTyCon tc = mkSynTy tc tys
+ | otherwise = mkTyConApp tc tys
+
mkTyConApp :: TyCon -> [Type] -> Type
+-- Assumes TyCon is not a SynTyCon; use mkSynTy instead for those
mkTyConApp tycon tys
- | isFunTyCon tycon && length tys == 2
- = case tys of
- (ty1:ty2:_) -> FunTy (mkUTyM ty1) (mkUTyM ty2)
+ | isFunTyCon tycon, [ty1,ty2] <- tys
+ = FunTy ty1 ty2
| otherwise
= ASSERT(not (isSynTyCon tycon))
- UASSERT2( not (any isUTy tys), ppr tycon <+> fsep (map pprType tys) )
TyConApp tycon tys
mkTyConTy :: TyCon -> Type
-mkTyConTy tycon = ASSERT( not (isSynTyCon tycon) )
- TyConApp tycon []
+mkTyConTy tycon = mkTyConApp tycon []
-- splitTyConApp "looks through" synonyms, because they don't
-- mean a distinct type, but all other type-constructor applications
-- including functions are returned as Just ..
tyConAppTyCon :: Type -> TyCon
-tyConAppTyCon ty = case splitTyConApp_maybe ty of
- Just (tc,_) -> tc
- Nothing -> pprPanic "tyConAppTyCon" (pprType ty)
+tyConAppTyCon ty = fst (splitTyConApp ty)
tyConAppArgs :: Type -> [Type]
-tyConAppArgs ty = case splitTyConApp_maybe ty of
- Just (_,args) -> args
- Nothing -> pprPanic "tyConAppArgs" (pprType ty)
+tyConAppArgs ty = snd (splitTyConApp ty)
splitTyConApp :: Type -> (TyCon, [Type])
splitTyConApp ty = case splitTyConApp_maybe ty of
Just stuff -> stuff
- Nothing -> pprPanic "splitTyConApp" (pprType ty)
+ Nothing -> pprPanic "splitTyConApp" (ppr ty)
splitTyConApp_maybe :: Type -> Maybe (TyCon, [Type])
+splitTyConApp_maybe ty | Just ty' <- coreView ty = splitTyConApp_maybe ty'
splitTyConApp_maybe (TyConApp tc tys) = Just (tc, tys)
-splitTyConApp_maybe (FunTy arg res) = Just (funTyCon, [unUTy arg,unUTy res])
-splitTyConApp_maybe (NoteTy _ ty) = splitTyConApp_maybe ty
-splitTyConApp_maybe (PredTy p) = splitTyConApp_maybe (predRepTy p)
-splitTyConApp_maybe (UsageTy _ ty) = splitTyConApp_maybe ty
+splitTyConApp_maybe (FunTy arg res) = Just (funTyCon, [arg,res])
splitTyConApp_maybe other = Nothing
-
--- splitAlgTyConApp_maybe looks for
--- *saturated* applications of *algebraic* data types
--- "Algebraic" => newtype, data type, or dictionary (not function types)
--- We return the constructors too, so there had better be some.
-
-splitAlgTyConApp_maybe :: Type -> Maybe (TyCon, [Type], [DataCon])
-splitAlgTyConApp_maybe (TyConApp tc tys)
- | isAlgTyCon tc &&
- tyConArity tc == length tys = Just (tc, tys, tyConDataCons tc)
-splitAlgTyConApp_maybe (NoteTy _ ty) = splitAlgTyConApp_maybe ty
-splitAlgTyConApp_maybe (PredTy p) = splitAlgTyConApp_maybe (predRepTy p)
-splitAlgTyConApp_maybe (UsageTy _ ty)= splitAlgTyConApp_maybe ty
-splitAlgTyConApp_maybe other = Nothing
-
-splitAlgTyConApp :: Type -> (TyCon, [Type], [DataCon])
- -- Here the "algebraic" property is an *assertion*
-splitAlgTyConApp (TyConApp tc tys) = ASSERT( isAlgTyCon tc && tyConArity tc == length tys )
- (tc, tys, tyConDataCons tc)
-splitAlgTyConApp (NoteTy _ ty) = splitAlgTyConApp ty
-splitAlgTyConApp (PredTy p) = splitAlgTyConApp (predRepTy p)
-splitAlgTyConApp (UsageTy _ ty) = splitAlgTyConApp ty
-#ifdef DEBUG
-splitAlgTyConApp ty = pprPanic "splitAlgTyConApp" (pprType ty)
-#endif
\end{code}
~~~~~
\begin{code}
-mkSynTy syn_tycon tys
- = ASSERT( isSynTyCon syn_tycon )
- ASSERT( length tyvars == length tys )
- NoteTy (SynNote (TyConApp syn_tycon tys))
- (substTy (mkTyVarSubst tyvars tys) body)
+mkSynTy tycon tys
+ | n_args == arity -- Exactly saturated
+ = mk_syn tys
+ | n_args > arity -- Over-saturated
+ = case splitAt arity tys of { (as,bs) -> mkAppTys (mk_syn as) bs }
+ -- Its important to use mkAppTys, rather than (foldl AppTy),
+ -- because (mk_syn as) might well return a partially-applied
+ -- type constructor; indeed, usually will!
+ | otherwise -- Un-saturated
+ = TyConApp tycon tys
+ -- For the un-saturated case we build TyConApp directly
+ -- (mkTyConApp ASSERTs that the tc isn't a SynTyCon).
+ -- Here we are relying on checkValidType to find
+ -- the error. What we can't do is use mkSynTy with
+ -- too few arg tys, because that is utterly bogus.
+
where
- (tyvars, body) = getSynTyConDefn syn_tycon
-
-deNoteType :: Type -> Type
- -- Remove synonyms, but not Preds
-deNoteType ty@(TyVarTy tyvar) = ty
-deNoteType (TyConApp tycon tys) = TyConApp tycon (map deNoteType tys)
-deNoteType (PredTy p) = PredTy (deNotePred p)
-deNoteType (NoteTy _ ty) = deNoteType ty
-deNoteType (AppTy fun arg) = AppTy (deNoteType fun) (deNoteType arg)
-deNoteType (FunTy fun arg) = FunTy (deNoteType fun) (deNoteType arg)
-deNoteType (ForAllTy tv ty) = ForAllTy tv (deNoteType ty)
-deNoteType (UsageTy u ty) = UsageTy u (deNoteType ty)
-
-deNotePred :: PredType -> PredType
-deNotePred (ClassP c tys) = ClassP c (map deNoteType tys)
-deNotePred (IParam n ty) = IParam n (deNoteType ty)
+ mk_syn tys = NoteTy (SynNote (TyConApp tycon tys))
+ (substTyWith tyvars tys body)
+
+ (tyvars, body) = ASSERT( isSynTyCon tycon ) getSynTyConDefn tycon
+ arity = tyConArity tycon
+ n_args = length tys
\end{code}
Notes on type synonyms
Representation types
~~~~~~~~~~~~~~~~~~~~
-
repType looks through
(a) for-alls, and
- (b) newtypes
- (c) synonyms
- (d) predicates
- (e) usage annotations
-It's useful in the back end where we're not
-interested in newtypes anymore.
+ (b) synonyms
+ (c) predicates
+ (d) usage annotations
+ (e) all newtypes, including recursive ones
+It's useful in the back end.
\begin{code}
repType :: Type -> Type
-repType (ForAllTy _ ty) = repType ty
-repType (NoteTy _ ty) = repType ty
-repType (PredTy p) = repType (predRepTy p)
-repType (UsageTy _ ty) = repType ty
-repType ty = case splitNewType_maybe ty of
- Just ty' -> repType ty' -- Still re-apply repType in case of for-all
- Nothing -> ty
-
-splitRepFunTys :: Type -> ([Type], Type)
--- Like splitFunTys, but looks through newtypes and for-alls
-splitRepFunTys ty = split [] (repType ty)
- where
- split args (FunTy arg res) = split (arg:args) (repType res)
- split args ty = (reverse args, ty)
-
+-- Only applied to types of kind *; hence tycons are saturated
+repType (ForAllTy _ ty) = repType ty
+repType (NoteTy _ ty) = repType ty
+repType (PredTy p) = repType (predTypeRep p)
+repType (TyConApp tc tys)
+ | isNewTyCon tc = ASSERT( tys `lengthIs` tyConArity tc )
+ repType (new_type_rep tc tys)
+repType ty = ty
+
+-- ToDo: this could be moved to the code generator, using splitTyConApp instead
+-- of inspecting the type directly.
typePrimRep :: Type -> PrimRep
typePrimRep ty = case repType ty of
TyConApp tc _ -> tyConPrimRep tc
FunTy _ _ -> PtrRep
- AppTy _ _ -> PtrRep -- ??
+ AppTy _ _ -> PtrRep -- See note below
TyVarTy _ -> PtrRep
-
-splitNewType_maybe :: Type -> Maybe Type
--- Find the representation of a newtype, if it is one
--- Looks through multiple levels of newtype, but does not look through for-alls
-splitNewType_maybe (NoteTy _ ty) = splitNewType_maybe ty
-splitNewType_maybe (PredTy p) = splitNewType_maybe (predRepTy p)
-splitNewType_maybe (UsageTy _ ty) = splitNewType_maybe ty
-splitNewType_maybe (TyConApp tc tys) = case newTyConRep tc of
- Just rep_ty -> ASSERT( length tys == tyConArity tc )
- -- The assert should hold because repType should
- -- only be applied to *types* (of kind *)
- Just (applyTys rep_ty tys)
- Nothing -> Nothing
-splitNewType_maybe other = Nothing
+ other -> pprPanic "typePrimRep" (ppr ty)
+ -- Types of the form 'f a' must be of kind *, not *#, so
+ -- we are guaranteed that they are represented by pointers.
+ -- The reason is that f must have kind *->*, not *->*#, because
+ -- (we claim) there is no way to constrain f's kind any other
+ -- way.
+
+-- new_type_rep doesn't ask any questions:
+-- it just expands newtype, whether recursive or not
+new_type_rep new_tycon tys = ASSERT( tys `lengthIs` tyConArity new_tycon )
+ case newTyConRep new_tycon of
+ (tvs, rep_ty) -> substTyWith tvs tys rep_ty
\end{code}
-
---------------------------------------------------------------------
ForAllTy
~~~~~~~~
= mkForAllTys [tyvar] ty
mkForAllTys :: [TyVar] -> Type -> Type
-mkForAllTys tyvars ty
- = case splitUTy_maybe ty of
- Just (u,ty1) -> UASSERT2( not (mkVarSet tyvars `intersectsVarSet` tyVarsOfType u),
- ptext SLIT("mkForAllTys: usage scope")
- <+> ppr tyvars <+> pprType ty )
- mkUTy u (foldr ForAllTy ty1 tyvars) -- we lift usage annotations over foralls
- Nothing -> foldr ForAllTy ty tyvars
+mkForAllTys tyvars ty = foldr ForAllTy ty tyvars
isForAllTy :: Type -> Bool
isForAllTy (NoteTy _ ty) = isForAllTy ty
isForAllTy (ForAllTy _ _) = True
-isForAllTy (UsageTy _ ty) = isForAllTy ty
isForAllTy other_ty = False
splitForAllTy_maybe :: Type -> Maybe (TyVar, Type)
splitForAllTy_maybe ty = splitFAT_m ty
where
- splitFAT_m (NoteTy _ ty) = splitFAT_m ty
- splitFAT_m (PredTy p) = splitFAT_m (predRepTy p)
- splitFAT_m (ForAllTy tyvar ty) = Just(tyvar, ty)
- splitFAT_m (UsageTy _ ty) = splitFAT_m ty
- splitFAT_m _ = Nothing
+ splitFAT_m ty | Just ty' <- coreView ty = splitFAT_m ty'
+ splitFAT_m (ForAllTy tyvar ty) = Just(tyvar, ty)
+ splitFAT_m _ = Nothing
splitForAllTys :: Type -> ([TyVar], Type)
splitForAllTys ty = split ty ty []
where
- split orig_ty (ForAllTy tv ty) tvs = split ty ty (tv:tvs)
- split orig_ty (NoteTy _ ty) tvs = split orig_ty ty tvs
- split orig_ty (PredTy p) tvs = split orig_ty (predRepTy p) tvs
- split orig_ty (UsageTy _ ty) tvs = split orig_ty ty tvs
- split orig_ty t tvs = (reverse tvs, orig_ty)
+ split orig_ty ty tvs | Just ty' <- coreView ty = split orig_ty ty' tvs
+ split orig_ty (ForAllTy tv ty) tvs = split ty ty (tv:tvs)
+ split orig_ty t tvs = (reverse tvs, orig_ty)
+
+dropForAlls :: Type -> Type
+dropForAlls ty = snd (splitForAllTys ty)
\end{code}
-- (mkPiType now in CoreUtils)
-Applying a for-all to its arguments. Lift usage annotation as required.
+applyTy, applyTys
+~~~~~~~~~~~~~~~~~
+Instantiate a for-all type with one or more type arguments.
+Used when we have a polymorphic function applied to type args:
+ f t1 t2
+Then we use (applyTys type-of-f [t1,t2]) to compute the type of
+the expression.
\begin{code}
applyTy :: Type -> Type -> Type
-applyTy (PredTy p) arg = applyTy (predRepTy p) arg
-applyTy (NoteTy _ fun) arg = applyTy fun arg
-applyTy (ForAllTy tv ty) arg = UASSERT2( not (isUTy arg),
- ptext SLIT("applyTy")
- <+> pprType ty <+> pprType arg )
- substTy (mkTyVarSubst [tv] [arg]) ty
-applyTy (UsageTy u ty) arg = UsageTy u (applyTy ty arg)
-applyTy other arg = panic "applyTy"
+applyTy ty arg | Just ty' <- coreView ty = applyTy ty' arg
+applyTy (ForAllTy tv ty) arg = substTyWith [tv] [arg] ty
+applyTy other arg = panic "applyTy"
applyTys :: Type -> [Type] -> Type
-applyTys fun_ty arg_tys
- = UASSERT2( not (any isUTy arg_tys), ptext SLIT("applyTys") <+> pprType fun_ty )
- (case mu of
- Just u -> UsageTy u
- Nothing -> id) $
- substTy (mkTyVarSubst tvs arg_tys) ty
- where
- (mu, tvs, ty) = split fun_ty arg_tys
-
- split fun_ty [] = (Nothing, [], fun_ty)
- split (NoteTy _ fun_ty) args = split fun_ty args
- split (PredTy p) args = split (predRepTy p) args
- split (ForAllTy tv fun_ty) (arg:args) = case split fun_ty args of
- (mu, tvs, ty) -> (mu, tv:tvs, ty)
- split (UsageTy u ty) args = case split ty args of
- (Nothing, tvs, ty) -> (Just u, tvs, ty)
- (Just _ , _ , _ ) -> pprPanic "applyTys:"
- (pprType fun_ty)
- split other_ty args = panic "applyTys"
-\end{code}
-
-\begin{code}
-hoistForAllTys :: Type -> Type
- -- Move all the foralls to the top
- -- e.g. T -> forall a. a ==> forall a. T -> a
- -- Careful: LOSES USAGE ANNOTATIONS!
-hoistForAllTys ty
- = case hoist ty of { (tvs, body) -> mkForAllTys tvs body }
+-- This function is interesting because
+-- a) the function may have more for-alls than there are args
+-- b) less obviously, it may have fewer for-alls
+-- For case (b) think of
+-- applyTys (forall a.a) [forall b.b, Int]
+-- This really can happen, via dressing up polymorphic types with newtype
+-- clothing. Here's an example:
+-- newtype R = R (forall a. a->a)
+-- foo = case undefined :: R of
+-- R f -> f ()
+
+applyTys orig_fun_ty [] = orig_fun_ty
+applyTys orig_fun_ty arg_tys
+ | n_tvs == n_args -- The vastly common case
+ = substTyWith tvs arg_tys rho_ty
+ | n_tvs > n_args -- Too many for-alls
+ = substTyWith (take n_args tvs) arg_tys
+ (mkForAllTys (drop n_args tvs) rho_ty)
+ | otherwise -- Too many type args
+ = ASSERT2( n_tvs > 0, ppr orig_fun_ty ) -- Zero case gives infnite loop!
+ applyTys (substTyWith tvs (take n_tvs arg_tys) rho_ty)
+ (drop n_tvs arg_tys)
where
- hoist :: Type -> ([TyVar], Type)
- hoist ty = case splitFunTys ty of { (args, res) ->
- case splitForAllTys res of {
- ([], body) -> ([], ty) ;
- (tvs1, body1) -> case hoist body1 of { (tvs2,body2) ->
- (tvs1 ++ tvs2, mkFunTys args body2)
- }}}
-\end{code}
-
-
----------------------------------------------------------------------
- UsageTy
- ~~~~~~~
-
-Constructing and taking apart usage types.
-
-\begin{code}
-mkUTy :: Type -> Type -> Type
-mkUTy u ty
- = ASSERT2( typeKind u == usageTypeKind, ptext SLIT("mkUTy:") <+> pprType u <+> pprType ty )
- UASSERT2( not (isUTy ty), ptext SLIT("mkUTy:") <+> pprType u <+> pprType ty )
- -- if u == usMany then ty else : ToDo? KSW 2000-10
-#ifdef DO_USAGES
- UsageTy u ty
-#else
- ty
-#endif
-
-splitUTy :: Type -> (Type {- :: $ -}, Type)
-splitUTy orig_ty
- = case splitUTy_maybe orig_ty of
- Just (u,ty) -> (u,ty)
-#ifdef DO_USAGES
- Nothing -> pprPanic "splitUTy:" (pprType orig_ty)
-#else
- Nothing -> (usMany,orig_ty) -- default annotation ToDo KSW 2000-10
-#endif
-
-splitUTy_maybe :: Type -> Maybe (Type {- :: $ -}, Type)
-splitUTy_maybe (UsageTy u ty) = Just (u,ty)
-splitUTy_maybe (NoteTy _ ty) = splitUTy_maybe ty
-splitUTy_maybe other_ty = Nothing
-
-isUTy :: Type -> Bool
- -- has usage annotation
-isUTy = maybeToBool . splitUTy_maybe
-
-uaUTy :: Type -> Type
- -- extract annotation
-uaUTy = fst . splitUTy
-
-unUTy :: Type -> Type
- -- extract unannotated type
-unUTy = snd . splitUTy
-\end{code}
-
-\begin{code}
-liftUTy :: (Type -> Type) -> Type -> Type
- -- lift outer usage annot over operation on unannotated types
-liftUTy f ty
- = let
- (u,ty') = splitUTy ty
- in
- mkUTy u (f ty')
-\end{code}
-
-\begin{code}
-mkUTyM :: Type -> Type
- -- put TOP (no info) annotation on unannotated type
-mkUTyM ty = mkUTy usMany ty
-\end{code}
-
-\begin{code}
-isUsageKind :: Kind -> Bool
-isUsageKind k
- = ASSERT( typeKind k == superKind )
- k == usageTypeKind
-
-isUsage :: Type -> Bool
-isUsage ty
- = isUsageKind (typeKind ty)
-
-isUTyVar :: Var -> Bool
-isUTyVar v
- = isUsageKind (tyVarKind v)
+ (tvs, rho_ty) = splitForAllTys orig_fun_ty
+ n_tvs = length tvs
+ n_args = length arg_tys
\end{code}
%************************************************************************
%* *
-\subsection{Predicates}
+\subsection{Source types}
%* *
%************************************************************************
-"Dictionary" types are just ordinary data types, but you can
-tell from the type constructor whether it's a dictionary or not.
-
-\begin{code}
-mkClassPred clas tys = UASSERT2( not (any isUTy tys), ppr clas <+> fsep (map pprType tys) )
- ClassP clas tys
-
-isClassPred (ClassP clas tys) = True
-isClassPred other = False
+A "source type" is a type that is a separate type as far as the type checker is
+concerned, but which has low-level representation as far as the back end is concerned.
-isIPPred (IParam _ _) = True
-isIPPred other = False
+Source types are always lifted.
-isTyVarClassPred (ClassP clas tys) = all isTyVarTy tys
-isTyVarClassPred other = False
-
-getClassPredTys_maybe :: PredType -> Maybe (Class, [Type])
-getClassPredTys_maybe (ClassP clas tys) = Just (clas, tys)
-getClassPredTys_maybe _ = Nothing
-
-getClassPredTys :: PredType -> (Class, [Type])
-getClassPredTys (ClassP clas tys) = (clas, tys)
-
-inheritablePred :: PredType -> Bool
--- Can be inherited by a context. For example, consider
--- f x = let g y = (?v, y+x)
--- in (g 3 with ?v = 8,
--- g 4 with ?v = 9)
--- The point is that g's type must be quantifed over ?v:
--- g :: (?v :: a) => a -> a
--- but it doesn't need to be quantified over the Num a dictionary
--- which can be free in g's rhs, and shared by both calls to g
-inheritablePred (ClassP _ _) = True
-inheritablePred other = False
-
-predMentionsIPs :: PredType -> NameSet -> Bool
-predMentionsIPs (IParam n _) ns = n `elemNameSet` ns
-predMentionsIPs other ns = False
-
-mkDictTy :: Class -> [Type] -> Type
-mkDictTy clas tys = UASSERT2( not (any isUTy tys), ppr clas <+> fsep (map pprType tys) )
- mkPredTy (ClassP clas tys)
+The key function is predTypeRep which gives the representation of a source type:
+\begin{code}
mkPredTy :: PredType -> Type
mkPredTy pred = PredTy pred
mkPredTys :: ThetaType -> [Type]
mkPredTys preds = map PredTy preds
-predTyUnique :: PredType -> Unique
-predTyUnique (IParam n _) = getUnique n
-predTyUnique (ClassP clas tys) = getUnique clas
-
-predRepTy :: PredType -> Type
--- Convert a predicate to its "representation type";
--- the type of evidence for that predicate, which is actually passed at runtime
-predRepTy (ClassP clas tys) = TyConApp (classTyCon clas) tys
-predRepTy (IParam n ty) = ty
-
-isPredTy :: Type -> Bool
-isPredTy (NoteTy _ ty) = isPredTy ty
-isPredTy (PredTy _) = True
-isPredTy (UsageTy _ ty)= isPredTy ty
-isPredTy _ = False
-
-isDictTy :: Type -> Bool
-isDictTy (NoteTy _ ty) = isDictTy ty
-isDictTy (PredTy (ClassP _ _)) = True
-isDictTy (UsageTy _ ty) = isDictTy ty
-isDictTy other = False
-
-splitPredTy_maybe :: Type -> Maybe PredType
-splitPredTy_maybe (NoteTy _ ty) = splitPredTy_maybe ty
-splitPredTy_maybe (PredTy p) = Just p
-splitPredTy_maybe (UsageTy _ ty)= splitPredTy_maybe ty
-splitPredTy_maybe other = Nothing
-
-splitDictTy :: Type -> (Class, [Type])
-splitDictTy (NoteTy _ ty) = splitDictTy ty
-splitDictTy (PredTy (ClassP clas tys)) = (clas, tys)
-
-splitDictTy_maybe :: Type -> Maybe (Class, [Type])
-splitDictTy_maybe (NoteTy _ ty) = splitDictTy_maybe ty
-splitDictTy_maybe (PredTy (ClassP clas tys)) = Just (clas, tys)
-splitDictTy_maybe other = Nothing
-
-splitDFunTy :: Type -> ([TyVar], [PredType], Class, [Type])
--- Split the type of a dictionary function
-splitDFunTy ty
- = case splitSigmaTy ty of { (tvs, theta, tau) ->
- case splitDictTy tau of { (clas, tys) ->
- (tvs, theta, clas, tys) }}
-
-mkPredName :: Unique -> SrcLoc -> PredType -> Name
-mkPredName uniq loc (ClassP cls tys) = mkLocalName uniq (mkDictOcc (getOccName cls)) loc
-mkPredName uniq loc (IParam name ty) = name
+predTypeRep :: PredType -> Type
+-- Convert a PredType to its "representation type";
+-- the post-type-checking type used by all the Core passes of GHC.
+-- Unwraps only the outermost level; for example, the result might
+-- be a newtype application
+predTypeRep (IParam _ ty) = ty
+predTypeRep (ClassP clas tys) = mkTyConApp (classTyCon clas) tys
+ -- Result might be a newtype application, but the consumer will
+ -- look through that too if necessary
\end{code}
+
%************************************************************************
%* *
-\subsection{Tau, sigma and rho}
+ NewTypes
%* *
%************************************************************************
-@isTauTy@ tests for nested for-alls.
-
-\begin{code}
-isTauTy :: Type -> Bool
-isTauTy (TyVarTy v) = True
-isTauTy (TyConApp _ tys) = all isTauTy tys
-isTauTy (AppTy a b) = isTauTy a && isTauTy b
-isTauTy (FunTy a b) = isTauTy a && isTauTy b
-isTauTy (PredTy p) = isTauTy (predRepTy p)
-isTauTy (NoteTy _ ty) = isTauTy ty
-isTauTy (UsageTy _ ty) = isTauTy ty
-isTauTy other = False
-\end{code}
-
\begin{code}
-mkRhoTy :: [PredType] -> Type -> Type
-mkRhoTy theta ty = UASSERT2( not (isUTy ty), pprType ty )
- foldr (\p r -> FunTy (mkUTyM (mkPredTy p)) (mkUTyM r)) ty theta
-
-splitRhoTy :: Type -> ([PredType], Type)
-splitRhoTy ty = split ty ty []
- where
- split orig_ty (FunTy arg res) ts = case splitPredTy_maybe arg of
- Just p -> split res res (p:ts)
- Nothing -> (reverse ts, orig_ty)
- split orig_ty (NoteTy _ ty) ts = split orig_ty ty ts
- split orig_ty (UsageTy _ ty) ts = split orig_ty ty ts
- split orig_ty ty ts = (reverse ts, orig_ty)
-\end{code}
-
-The type of a method for class C is always of the form:
- Forall a1..an. C a1..an => sig_ty
-where sig_ty is the type given by the method's signature, and thus in general
-is a ForallTy. At the point that splitMethodTy is called, it is expected
-that the outer Forall has already been stripped off. splitMethodTy then
-returns (C a1..an, sig_ty') where sig_ty' is sig_ty with any Notes or
-Usages stripped off.
-
-\begin{code}
-splitMethodTy :: Type -> (PredType, Type)
-splitMethodTy ty = split ty
- where
- split (FunTy arg res) = case splitPredTy_maybe arg of
- Just p -> (p, res)
- Nothing -> panic "splitMethodTy"
- split (NoteTy _ ty) = split ty
- split (UsageTy _ ty) = split ty
- split _ = panic "splitMethodTy"
-\end{code}
-
-
-isSigmaType returns true of any qualified type. It doesn't *necessarily* have
-any foralls. E.g.
- f :: (?x::Int) => Int -> Int
-
-\begin{code}
-mkSigmaTy tyvars theta tau = mkForAllTys tyvars (mkRhoTy theta tau)
-
-isSigmaTy :: Type -> Bool
-isSigmaTy (ForAllTy tyvar ty) = True
-isSigmaTy (FunTy a b) = isPredTy a
-isSigmaTy (NoteTy _ ty) = isSigmaTy ty
-isSigmaTy (UsageTy _ ty) = isSigmaTy ty
-isSigmaTy _ = False
-
-splitSigmaTy :: Type -> ([TyVar], [PredType], Type)
-splitSigmaTy ty =
- (tyvars, theta, tau)
- where
- (tyvars,rho) = splitForAllTys ty
- (theta,tau) = splitRhoTy rho
-\end{code}
-
-\begin{code}
-getDFunTyKey :: Type -> OccName -- Get some string from a type, to be used to
- -- construct a dictionary function name
-getDFunTyKey (TyVarTy tv) = getOccName tv
-getDFunTyKey (TyConApp tc _) = getOccName tc
-getDFunTyKey (AppTy fun _) = getDFunTyKey fun
-getDFunTyKey (NoteTy _ t) = getDFunTyKey t
-getDFunTyKey (FunTy arg _) = getOccName funTyCon
-getDFunTyKey (ForAllTy _ t) = getDFunTyKey t
-getDFunTyKey (UsageTy _ t) = getDFunTyKey t
--- PredTy shouldn't happen
+splitRecNewType_maybe :: Type -> Maybe Type
+-- Sometimes we want to look through a recursive newtype, and that's what happens here
+-- It only strips *one layer* off, so the caller will usually call itself recursively
+-- Only applied to types of kind *, hence the newtype is always saturated
+splitRecNewType_maybe ty | Just ty' <- coreView ty = splitRecNewType_maybe ty'
+splitRecNewType_maybe (TyConApp tc tys)
+ | isNewTyCon tc
+ = ASSERT( tys `lengthIs` tyConArity tc ) -- splitRecNewType_maybe only be applied
+ -- to *types* (of kind *)
+ ASSERT( isRecursiveTyCon tc ) -- Guaranteed by coreView
+ case newTyConRhs tc of
+ (tvs, rep_ty) -> Just (substTyWith tvs tys rep_ty)
+
+splitRecNewType_maybe other = Nothing
\end{code}
typeKind :: Type -> Kind
typeKind (TyVarTy tyvar) = tyVarKind tyvar
-typeKind (TyConApp tycon tys) = foldr (\_ k -> funResultTy k) (tyConKind tycon) tys
+typeKind (TyConApp tycon tys) = foldr (\_ k -> kindFunResult k) (tyConKind tycon) tys
typeKind (NoteTy _ ty) = typeKind ty
typeKind (PredTy _) = liftedTypeKind -- Predicates are always
-- represented by lifted types
-typeKind (AppTy fun arg) = funResultTy (typeKind fun)
-
-typeKind (FunTy arg res) = fix_up (typeKind res)
- where
- fix_up (TyConApp tycon _) | tycon == typeCon
- || tycon == openKindCon = liftedTypeKind
- fix_up (NoteTy _ kind) = fix_up kind
- fix_up kind = kind
- -- The basic story is
- -- typeKind (FunTy arg res) = typeKind res
- -- But a function is lifted regardless of its result type
- -- Hence the strange fix-up.
- -- Note that 'res', being the result of a FunTy, can't have
- -- a strange kind like (*->*).
-
+typeKind (AppTy fun arg) = kindFunResult (typeKind fun)
+typeKind (FunTy arg res) = liftedTypeKind
typeKind (ForAllTy tv ty) = typeKind ty
-typeKind (UsageTy _ ty) = typeKind ty -- we don't have separate kinds for ann/unann
\end{code}
Free variables of a type
~~~~~~~~~~~~~~~~~~~~~~~~
\begin{code}
-
tyVarsOfType :: Type -> TyVarSet
tyVarsOfType (TyVarTy tv) = unitVarSet tv
tyVarsOfType (TyConApp tycon tys) = tyVarsOfTypes tys
tyVarsOfType (NoteTy (FTVNote tvs) ty2) = tvs
-tyVarsOfType (NoteTy (SynNote ty1) ty2) = tyVarsOfType ty1
-tyVarsOfType (PredTy p) = tyVarsOfPred p
+tyVarsOfType (NoteTy (SynNote ty1) ty2) = tyVarsOfType ty2 -- See note [Syn] below
+tyVarsOfType (PredTy sty) = tyVarsOfPred sty
tyVarsOfType (FunTy arg res) = tyVarsOfType arg `unionVarSet` tyVarsOfType res
tyVarsOfType (AppTy fun arg) = tyVarsOfType fun `unionVarSet` tyVarsOfType arg
tyVarsOfType (ForAllTy tyvar ty) = tyVarsOfType ty `minusVarSet` unitVarSet tyvar
-tyVarsOfType (UsageTy u ty) = tyVarsOfType u `unionVarSet` tyVarsOfType ty
+
+-- Note [Syn]
+-- Consider
+-- type T a = Int
+-- What are the free tyvars of (T x)? Empty, of course!
+-- Here's the example that Ralf Laemmel showed me:
+-- foo :: (forall a. C u a -> C u a) -> u
+-- mappend :: Monoid u => u -> u -> u
+--
+-- bar :: Monoid u => u
+-- bar = foo (\t -> t `mappend` t)
+-- We have to generalise at the arg to f, and we don't
+-- want to capture the constraint (Monad (C u a)) because
+-- it appears to mention a. Pretty silly, but it was useful to him.
+
tyVarsOfTypes :: [Type] -> TyVarSet
tyVarsOfTypes tys = foldr (unionVarSet.tyVarsOfType) emptyVarSet tys
tyVarsOfPred :: PredType -> TyVarSet
-tyVarsOfPred (ClassP clas tys) = tyVarsOfTypes tys
-tyVarsOfPred (IParam n ty) = tyVarsOfType ty
+tyVarsOfPred (IParam _ ty) = tyVarsOfType ty
+tyVarsOfPred (ClassP _ tys) = tyVarsOfTypes tys
tyVarsOfTheta :: ThetaType -> TyVarSet
tyVarsOfTheta = foldr (unionVarSet . tyVarsOfPred) emptyVarSet
addFreeTyVars :: Type -> Type
addFreeTyVars ty@(NoteTy (FTVNote _) _) = ty
addFreeTyVars ty = NoteTy (FTVNote (tyVarsOfType ty)) ty
-
--- Find the free names of a type, including the type constructors and classes it mentions
-namesOfType :: Type -> NameSet
-namesOfType (TyVarTy tv) = unitNameSet (getName tv)
-namesOfType (TyConApp tycon tys) = unitNameSet (getName tycon) `unionNameSets`
- namesOfTypes tys
-namesOfType (NoteTy (SynNote ty1) ty2) = namesOfType ty1
-namesOfType (NoteTy other_note ty2) = namesOfType ty2
-namesOfType (PredTy p) = namesOfType (predRepTy p)
-namesOfType (FunTy arg res) = namesOfType arg `unionNameSets` namesOfType res
-namesOfType (AppTy fun arg) = namesOfType fun `unionNameSets` namesOfType arg
-namesOfType (ForAllTy tyvar ty) = namesOfType ty `delFromNameSet` getName tyvar
-namesOfType (UsageTy u ty) = namesOfType u `unionNameSets` namesOfType ty
-
-namesOfTypes tys = foldr (unionNameSets . namesOfType) emptyNameSet tys
\end{code}
-Usage annotations of a type
-~~~~~~~~~~~~~~~~~~~~~~~~~~~
-
-Get a list of usage annotations of a type, *in left-to-right pre-order*.
-
-\begin{code}
-usageAnnOfType :: Type -> [Type]
-usageAnnOfType ty
- = goS ty
- where
- goT (TyVarTy _) = []
- goT (AppTy ty1 ty2) = goT ty1 ++ goT ty2
- goT (TyConApp tc tys) = concatMap goT tys
- goT (FunTy sty1 sty2) = goS sty1 ++ goS sty2
- goT (ForAllTy mv ty) = goT ty
- goT (PredTy p) = goT (predRepTy p)
- goT ty@(UsageTy _ _) = pprPanic "usageAnnOfType: unexpected usage:" (pprType ty)
- goT (NoteTy note ty) = goT ty
-
- goS sty = case splitUTy sty of
- (u,tty) -> u : goT tty
-\end{code}
-
-
%************************************************************************
%* *
\subsection{TidyType}
It doesn't change the uniques at all, just the print names.
\begin{code}
-tidyTyVar :: TidyEnv -> TyVar -> (TidyEnv, TyVar)
-tidyTyVar env@(tidy_env, subst) tyvar
- = case lookupVarEnv subst tyvar of
-
- Just tyvar' -> -- Already substituted
- (env, tyvar')
-
- Nothing -> -- Make a new nice name for it
-
- case tidyOccName tidy_env (getOccName name) of
- (tidy', occ') -> -- New occname reqd
- ((tidy', subst'), tyvar')
- where
- subst' = extendVarEnv subst tyvar tyvar'
- tyvar' = setTyVarName tyvar name'
- name' = mkLocalName (getUnique name) occ' noSrcLoc
- -- Note: make a *user* tyvar, so it printes nicely
- -- Could extract src loc, but no need.
+tidyTyVarBndr :: TidyEnv -> TyVar -> (TidyEnv, TyVar)
+tidyTyVarBndr (tidy_env, subst) tyvar
+ = case tidyOccName tidy_env (getOccName name) of
+ (tidy', occ') -> ((tidy', subst'), tyvar')
+ where
+ subst' = extendVarEnv subst tyvar tyvar'
+ tyvar' = setTyVarName tyvar name'
+ name' = mkInternalName (getUnique name) occ' noSrcLoc
+ -- Note: make a *user* tyvar, so it printes nicely
+ -- Could extract src loc, but no need.
where
name = tyVarName tyvar
-tidyTyVars :: TidyEnv -> [TyVar] -> (TidyEnv, [TyVar])
-tidyTyVars env tyvars = mapAccumL tidyTyVar env tyvars
-
tidyFreeTyVars :: TidyEnv -> TyVarSet -> TidyEnv
-- Add the free tyvars to the env in tidy form,
-- so that we can tidy the type they are free in
-tidyFreeTyVars env tyvars = foldl add env (varSetElems tyvars)
- where
- add env tv = fst (tidyTyVar env tv)
+tidyFreeTyVars env tyvars = fst (tidyOpenTyVars env (varSetElems tyvars))
+
+tidyOpenTyVars :: TidyEnv -> [TyVar] -> (TidyEnv, [TyVar])
+tidyOpenTyVars env tyvars = mapAccumL tidyOpenTyVar env tyvars
+
+tidyOpenTyVar :: TidyEnv -> TyVar -> (TidyEnv, TyVar)
+-- Treat a new tyvar as a binder, and give it a fresh tidy name
+tidyOpenTyVar env@(tidy_env, subst) tyvar
+ = case lookupVarEnv subst tyvar of
+ Just tyvar' -> (env, tyvar') -- Already substituted
+ Nothing -> tidyTyVarBndr env tyvar -- Treat it as a binder
tidyType :: TidyEnv -> Type -> Type
tidyType env@(tidy_env, subst) ty
Just tv' -> TyVarTy tv'
go (TyConApp tycon tys) = let args = map go tys
in args `seqList` TyConApp tycon args
- go (NoteTy note ty) = (NoteTy SAPPLY (go_note note)) SAPPLY (go ty)
- go (PredTy p) = PredTy (tidyPred env p)
- go (AppTy fun arg) = (AppTy SAPPLY (go fun)) SAPPLY (go arg)
- go (FunTy fun arg) = (FunTy SAPPLY (go fun)) SAPPLY (go arg)
- go (ForAllTy tv ty) = ForAllTy tvp SAPPLY (tidyType envp ty)
+ go (NoteTy note ty) = (NoteTy $! (go_note note)) $! (go ty)
+ go (PredTy sty) = PredTy (tidyPred env sty)
+ go (AppTy fun arg) = (AppTy $! (go fun)) $! (go arg)
+ go (FunTy fun arg) = (FunTy $! (go fun)) $! (go arg)
+ go (ForAllTy tv ty) = ForAllTy tvp $! (tidyType envp ty)
where
- (envp, tvp) = tidyTyVar env tv
- go (UsageTy u ty) = (UsageTy SAPPLY (go u)) SAPPLY (go ty)
+ (envp, tvp) = tidyTyVarBndr env tv
- go_note (SynNote ty) = SynNote SAPPLY (go ty)
+ go_note (SynNote ty) = SynNote $! (go ty)
go_note note@(FTVNote ftvs) = note -- No need to tidy the free tyvars
tidyTypes env tys = map (tidyType env) tys
tidyPred :: TidyEnv -> PredType -> PredType
-tidyPred env (ClassP clas tys) = ClassP clas (tidyTypes env tys)
tidyPred env (IParam n ty) = IParam n (tidyType env ty)
+tidyPred env (ClassP clas tys) = ClassP clas (tidyTypes env tys)
\end{code}
-- They are pretty bogus types, mind you. It would be better never to
-- construct them
-isUnLiftedType (ForAllTy tv ty) = isUnLiftedType ty
-isUnLiftedType (NoteTy _ ty) = isUnLiftedType ty
-isUnLiftedType (TyConApp tc _) = isUnLiftedTyCon tc
-isUnLiftedType (UsageTy _ ty) = isUnLiftedType ty
-isUnLiftedType other = False
+isUnLiftedType ty | Just ty' <- coreView ty = isUnLiftedType ty'
+isUnLiftedType (ForAllTy tv ty) = isUnLiftedType ty
+isUnLiftedType (TyConApp tc _) = isUnLiftedTyCon tc
+isUnLiftedType other = False
isUnboxedTupleType :: Type -> Bool
isUnboxedTupleType ty = case splitTyConApp_maybe ty of
-- Should only be applied to *types*; hence the assert
isAlgType :: Type -> Bool
isAlgType ty = case splitTyConApp_maybe ty of
- Just (tc, ty_args) -> ASSERT( length ty_args == tyConArity tc )
+ Just (tc, ty_args) -> ASSERT( ty_args `lengthIs` tyConArity tc )
isAlgTyCon tc
other -> False
+\end{code}
--- Should only be applied to *types*; hence the assert
-isDataType :: Type -> Bool
-isDataType ty = case splitTyConApp_maybe ty of
- Just (tc, ty_args) -> ASSERT( length ty_args == tyConArity tc )
- isDataTyCon tc
- other -> False
+@isStrictType@ computes whether an argument (or let RHS) should
+be computed strictly or lazily, based only on its type.
+Works just like isUnLiftedType, except that it has a special case
+for dictionaries. Since it takes account of ClassP, you might think
+this function should be in TcType, but isStrictType is used by DataCon,
+which is below TcType in the hierarchy, so it's convenient to put it here.
+
+\begin{code}
+isStrictType (PredTy pred) = isStrictPred pred
+isStrictType ty | Just ty' <- coreView ty = isStrictType ty'
+isStrictType (ForAllTy tv ty) = isStrictType ty
+isStrictType (TyConApp tc _) = isUnLiftedTyCon tc
+isStrictType other = False
+
+isStrictPred (ClassP clas _) = opt_DictsStrict && not (isNewTyCon (classTyCon clas))
+isStrictPred other = False
+ -- We may be strict in dictionary types, but only if it
+ -- has more than one component.
+ -- [Being strict in a single-component dictionary risks
+ -- poking the dictionary component, which is wrong.]
+\end{code}
-isNewType :: Type -> Bool
-isNewType ty = case splitTyConApp_maybe ty of
- Just (tc, ty_args) -> ASSERT( length ty_args == tyConArity tc )
- isNewTyCon tc
+\begin{code}
+isPrimitiveType :: Type -> Bool
+-- Returns types that are opaque to Haskell.
+-- Most of these are unlifted, but now that we interact with .NET, we
+-- may have primtive (foreign-imported) types that are lifted
+isPrimitiveType ty = case splitTyConApp_maybe ty of
+ Just (tc, ty_args) -> ASSERT( ty_args `lengthIs` tyConArity tc )
+ isPrimTyCon tc
other -> False
\end{code}
seqType (PredTy p) = seqPred p
seqType (TyConApp tc tys) = tc `seq` seqTypes tys
seqType (ForAllTy tv ty) = tv `seq` seqType ty
-seqType (UsageTy u ty) = seqType u `seq` seqType ty
seqTypes :: [Type] -> ()
seqTypes [] = ()
seqNote (FTVNote set) = sizeUniqSet set `seq` ()
seqPred :: PredType -> ()
-seqPred (ClassP c tys) = c `seq` seqTypes tys
-seqPred (IParam n ty) = n `seq` seqType ty
+seqPred (ClassP c tys) = c `seq` seqTypes tys
+seqPred (IParam n ty) = n `seq` seqType ty
\end{code}
%************************************************************************
%* *
-\subsection{Equality on types}
+ Comparison of types
+ (We don't use instances so that we know where it happens)
%* *
%************************************************************************
+Two flavours:
+
+* tcEqType, tcCmpType do *not* look through newtypes, PredTypes
+* coreEqType *does* look through them
+
+Note that eqType can respond 'False' for partial applications of newtypes.
+Consider
+ newtype Parser m a = MkParser (Foogle m a)
+Does
+ Monad (Parser m) `eqType` Monad (Foogle m)
+Well, yes, but eqType won't see that they are the same.
+I don't think this is harmful, but it's soemthing to watch out for.
+
+First, the external interface
\begin{code}
-instance Eq Type where
- ty1 == ty2 = case ty1 `compare` ty2 of { EQ -> True; other -> False }
-
-instance Ord Type where
- compare ty1 ty2 = cmpTy emptyVarEnv ty1 ty2
-
-cmpTy :: TyVarEnv TyVar -> Type -> Type -> Ordering
- -- The "env" maps type variables in ty1 to type variables in ty2
- -- So when comparing for-alls.. (forall tv1 . t1) (forall tv2 . t2)
- -- we in effect substitute tv2 for tv1 in t1 before continuing
-
- -- Get rid of NoteTy
-cmpTy env (NoteTy _ ty1) ty2 = cmpTy env ty1 ty2
-cmpTy env ty1 (NoteTy _ ty2) = cmpTy env ty1 ty2
-
- -- Get rid of PredTy
-cmpTy env (PredTy p1) (PredTy p2) = cmpPred env p1 p2
-cmpTy env (PredTy p1) ty2 = cmpTy env (predRepTy p1) ty2
-cmpTy env ty1 (PredTy p2) = cmpTy env ty1 (predRepTy p2)
-
- -- Deal with equal constructors
-cmpTy env (TyVarTy tv1) (TyVarTy tv2) = case lookupVarEnv env tv1 of
- Just tv1a -> tv1a `compare` tv2
- Nothing -> tv1 `compare` tv2
-
-cmpTy env (AppTy f1 a1) (AppTy f2 a2) = cmpTy env f1 f2 `thenCmp` cmpTy env a1 a2
-cmpTy env (FunTy f1 a1) (FunTy f2 a2) = cmpTy env f1 f2 `thenCmp` cmpTy env a1 a2
-cmpTy env (TyConApp tc1 tys1) (TyConApp tc2 tys2) = (tc1 `compare` tc2) `thenCmp` (cmpTys env tys1 tys2)
-cmpTy env (ForAllTy tv1 t1) (ForAllTy tv2 t2) = cmpTy (extendVarEnv env tv1 tv2) t1 t2
-cmpTy env (UsageTy u1 t1) (UsageTy u2 t2) = cmpTy env u1 u2 `thenCmp` cmpTy env t1 t2
-
- -- Deal with the rest: TyVarTy < AppTy < FunTy < TyConApp < ForAllTy < UsageTy
-cmpTy env (AppTy _ _) (TyVarTy _) = GT
-
-cmpTy env (FunTy _ _) (TyVarTy _) = GT
-cmpTy env (FunTy _ _) (AppTy _ _) = GT
-
-cmpTy env (TyConApp _ _) (TyVarTy _) = GT
-cmpTy env (TyConApp _ _) (AppTy _ _) = GT
-cmpTy env (TyConApp _ _) (FunTy _ _) = GT
-
-cmpTy env (ForAllTy _ _) (TyVarTy _) = GT
-cmpTy env (ForAllTy _ _) (AppTy _ _) = GT
-cmpTy env (ForAllTy _ _) (FunTy _ _) = GT
-cmpTy env (ForAllTy _ _) (TyConApp _ _) = GT
+coreEqType :: Type -> Type -> Bool
+coreEqType t1 t2 = isEqual $ cmpType (deepCoreView t1) (deepCoreView t2)
-cmpTy env (UsageTy _ _) other = GT
-
-cmpTy env _ _ = LT
+tcEqType :: Type -> Type -> Bool
+tcEqType t1 t2 = isEqual $ cmpType t1 t2
+
+tcEqTypes :: [Type] -> [Type] -> Bool
+tcEqTypes tys1 tys2 = isEqual $ cmpTypes tys1 tys2
+
+tcCmpType :: Type -> Type -> Ordering
+tcCmpType t1 t2 = cmpType t1 t2
+
+tcCmpTypes :: [Type] -> [Type] -> Ordering
+tcCmpTypes tys1 tys2 = cmpTypes tys1 tys2
+
+tcEqPred :: PredType -> PredType -> Bool
+tcEqPred p1 p2 = isEqual $ cmpPred p1 p2
+tcCmpPred :: PredType -> PredType -> Ordering
+tcCmpPred p1 p2 = cmpPred p1 p2
-cmpTys env [] [] = EQ
-cmpTys env (t:ts) [] = GT
-cmpTys env [] (t:ts) = LT
-cmpTys env (t1:t1s) (t2:t2s) = cmpTy env t1 t2 `thenCmp` cmpTys env t1s t2s
+tcEqTypeX :: RnEnv2 -> Type -> Type -> Bool
+tcEqTypeX env t1 t2 = isEqual $ cmpTypeX env t1 t2
\end{code}
+Now here comes the real worker
+
\begin{code}
-instance Eq PredType where
- p1 == p2 = case p1 `compare` p2 of { EQ -> True; other -> False }
+cmpType :: Type -> Type -> Ordering
+cmpType t1 t2 = cmpTypeX rn_env t1 t2
+ where
+ rn_env = mkRnEnv2 (mkInScopeSet (tyVarsOfType t1 `unionVarSet` tyVarsOfType t2))
+
+cmpTypes :: [Type] -> [Type] -> Ordering
+cmpTypes ts1 ts2 = cmpTypesX rn_env ts1 ts2
+ where
+ rn_env = mkRnEnv2 (mkInScopeSet (tyVarsOfTypes ts1 `unionVarSet` tyVarsOfTypes ts2))
+
+cmpPred :: PredType -> PredType -> Ordering
+cmpPred p1 p2 = cmpPredX rn_env p1 p2
+ where
+ rn_env = mkRnEnv2 (mkInScopeSet (tyVarsOfPred p1 `unionVarSet` tyVarsOfPred p2))
+
+cmpTypeX :: RnEnv2 -> Type -> Type -> Ordering -- Main workhorse
+
+-- NB: we *cannot* short-cut the newtype comparison thus:
+-- eqTypeX env (NewTcApp tc1 tys1) (NewTcApp tc2 tys2)
+-- | (tc1 == tc2) = (eqTypeXs env tys1 tys2)
+--
+-- Consider:
+-- newtype T a = MkT [a]
+-- newtype Foo m = MkFoo (forall a. m a -> Int)
+-- w1 :: Foo []
+-- w1 = ...
+--
+-- w2 :: Foo T
+-- w2 = MkFoo (\(MkT x) -> case w1 of MkFoo f -> f x)
+--
+-- We end up with w2 = w1; so we need that Foo T = Foo []
+-- but we can only expand saturated newtypes, so just comparing
+-- T with [] won't do.
+
+cmpTypeX env (TyVarTy tv1) (TyVarTy tv2) = rnOccL env tv1 `compare` rnOccR env tv2
+cmpTypeX env (ForAllTy tv1 t1) (ForAllTy tv2 t2) = cmpTypeX (rnBndr2 env tv1 tv2) t1 t2
+cmpTypeX env (AppTy s1 t1) (AppTy s2 t2) = cmpTypeX env s1 s2 `thenCmp` cmpTypeX env t1 t2
+cmpTypeX env (FunTy s1 t1) (FunTy s2 t2) = cmpTypeX env s1 s2 `thenCmp` cmpTypeX env t1 t2
+cmpTypeX env (PredTy p1) (PredTy p2) = cmpPredX env p1 p2
+cmpTypeX env (TyConApp tc1 tys1) (TyConApp tc2 tys2) = (tc1 `compare` tc2) `thenCmp` cmpTypesX env tys1 tys2
+cmpTypeX env (NoteTy _ t1) t2 = cmpTypeX env t1 t2
+cmpTypeX env t1 (NoteTy _ t2) = cmpTypeX env t1 t2
+
+ -- Deal with the rest: TyVarTy < AppTy < FunTy < TyConApp < ForAllTy < PredTy
+cmpTypeX env (AppTy _ _) (TyVarTy _) = GT
+
+cmpTypeX env (FunTy _ _) (TyVarTy _) = GT
+cmpTypeX env (FunTy _ _) (AppTy _ _) = GT
+
+cmpTypeX env (TyConApp _ _) (TyVarTy _) = GT
+cmpTypeX env (TyConApp _ _) (AppTy _ _) = GT
+cmpTypeX env (TyConApp _ _) (FunTy _ _) = GT
+
+cmpTypeX env (ForAllTy _ _) (TyVarTy _) = GT
+cmpTypeX env (ForAllTy _ _) (AppTy _ _) = GT
+cmpTypeX env (ForAllTy _ _) (FunTy _ _) = GT
+cmpTypeX env (ForAllTy _ _) (TyConApp _ _) = GT
-instance Ord PredType where
- compare p1 p2 = cmpPred emptyVarEnv p1 p2
+cmpTypeX env (PredTy _) t2 = GT
-cmpPred :: TyVarEnv TyVar -> PredType -> PredType -> Ordering
-cmpPred env (IParam n1 ty1) (IParam n2 ty2) = (n1 `compare` n2) `thenCmp` (cmpTy env ty1 ty2)
+cmpTypeX env _ _ = LT
+
+-------------
+cmpTypesX :: RnEnv2 -> [Type] -> [Type] -> Ordering
+cmpTypesX env [] [] = EQ
+cmpTypesX env (t1:tys1) (t2:tys2) = cmpTypeX env t1 t2 `thenCmp` cmpTypesX env tys1 tys2
+cmpTypesX env [] tys = LT
+cmpTypesX env ty [] = GT
+
+-------------
+cmpPredX :: RnEnv2 -> PredType -> PredType -> Ordering
+cmpPredX env (IParam n1 ty1) (IParam n2 ty2) = (n1 `compare` n2) `thenCmp` cmpTypeX env ty1 ty2
-- Compare types as well as names for implicit parameters
-- This comparison is used exclusively (I think) for the
-- finite map built in TcSimplify
-cmpPred env (ClassP c1 tys1) (ClassP c2 tys2) = (c1 `compare` c2) `thenCmp` (cmpTys env tys1 tys2)
-cmpPred env (IParam _ _) (ClassP _ _) = LT
-cmpPred env (ClassP _ _) (IParam _ _) = GT
+cmpPredX env (ClassP c1 tys1) (ClassP c2 tys2) = (c1 `compare` c2) `thenCmp` cmpTypesX env tys1 tys2
+cmpPredX env (IParam _ _) (ClassP _ _) = LT
+cmpPredX env (ClassP _ _) (IParam _ _) = GT
+\end{code}
+
+PredTypes are used as a FM key in TcSimplify,
+so we take the easy path and make them an instance of Ord
+
+\begin{code}
+instance Eq PredType where { (==) = tcEqPred }
+instance Ord PredType where { compare = tcCmpPred }
\end{code}
+
+
+%************************************************************************
+%* *
+ Type substitutions
+%* *
+%************************************************************************
+
+\begin{code}
+data TvSubst
+ = TvSubst InScopeSet -- The in-scope type variables
+ TvSubstEnv -- The substitution itself; guaranteed idempotent
+ -- See Note [Apply Once]
+
+{- ----------------------------------------------------------
+ Note [Apply Once]
+
+We use TvSubsts to instantiate things, and we might instantiate
+ forall a b. ty
+\with the types
+ [a, b], or [b, a].
+So the substition might go [a->b, b->a]. A similar situation arises in Core
+when we find a beta redex like
+ (/\ a /\ b -> e) b a
+Then we also end up with a substition that permutes type variables. Other
+variations happen to; for example [a -> (a, b)].
+
+ ***************************************************
+ *** So a TvSubst must be applied precisely once ***
+ ***************************************************
+
+A TvSubst is not idempotent, but, unlike the non-idempotent substitution
+we use during unifications, it must not be repeatedly applied.
+-------------------------------------------------------------- -}
+
+
+type TvSubstEnv = TyVarEnv Type
+ -- A TvSubstEnv is used both inside a TvSubst (with the apply-once
+ -- invariant discussed in Note [Apply Once]), and also independently
+ -- in the middle of matching, and unification (see Types.Unify)
+ -- So you have to look at the context to know if it's idempotent or
+ -- apply-once or whatever
+
+emptyTvSubst = TvSubst emptyInScopeSet emptyVarEnv
+isEmptyTvSubst :: TvSubst -> Bool
+isEmptyTvSubst (TvSubst _ env) = isEmptyVarEnv env
+
+getTvSubstEnv :: TvSubst -> TvSubstEnv
+getTvSubstEnv (TvSubst _ env) = env
+
+getTvInScope :: TvSubst -> InScopeSet
+getTvInScope (TvSubst in_scope _) = in_scope
+
+isInScope :: Var -> TvSubst -> Bool
+isInScope v (TvSubst in_scope _) = v `elemInScopeSet` in_scope
+
+setTvSubstEnv :: TvSubst -> TvSubstEnv -> TvSubst
+setTvSubstEnv (TvSubst in_scope _) env = TvSubst in_scope env
+
+extendTvInScope :: TvSubst -> [Var] -> TvSubst
+extendTvInScope (TvSubst in_scope env) vars = TvSubst (extendInScopeSetList in_scope vars) env
+
+extendTvSubst :: TvSubst -> TyVar -> Type -> TvSubst
+extendTvSubst (TvSubst in_scope env) tv ty = TvSubst in_scope (extendVarEnv env tv ty)
+
+extendTvSubstList :: TvSubst -> [TyVar] -> [Type] -> TvSubst
+extendTvSubstList (TvSubst in_scope env) tvs tys
+ = TvSubst in_scope (extendVarEnvList env (tvs `zip` tys))
+
+-- mkTvSubst and zipTvSubst generate the in-scope set from
+-- the types given; but it's just a thunk so with a bit of luck
+-- it'll never be evaluated
+
+mkTvSubst :: TvSubstEnv -> TvSubst
+mkTvSubst env
+ = TvSubst (mkInScopeSet (tyVarsOfTypes (varEnvElts env))) env
+
+zipTvSubst :: [TyVar] -> [Type] -> TvSubst
+zipTvSubst tyvars tys
+ = TvSubst (mkInScopeSet (tyVarsOfTypes tys)) (zipTyEnv tyvars tys)
+
+-- mkTopTvSubst is called when doing top-level substitutions.
+-- Here we expect that the free vars of the range of the
+-- substitution will be empty.
+mkTopTvSubst :: [(TyVar, Type)] -> TvSubst
+mkTopTvSubst prs = TvSubst emptyInScopeSet (mkVarEnv prs)
+
+zipTopTvSubst :: [TyVar] -> [Type] -> TvSubst
+zipTopTvSubst tyvars tys = TvSubst emptyInScopeSet (zipTyEnv tyvars tys)
+
+zipTyEnv :: [TyVar] -> [Type] -> TvSubstEnv
+zipTyEnv tyvars tys
+#ifdef DEBUG
+ | length tyvars /= length tys
+ = pprTrace "mkTopTvSubst" (ppr tyvars $$ ppr tys) emptyVarEnv
+ | otherwise
+#endif
+ = zip_ty_env tyvars tys emptyVarEnv
+
+-- Later substitutions in the list over-ride earlier ones,
+-- but there should be no loops
+zip_ty_env [] [] env = env
+zip_ty_env (tv:tvs) (ty:tys) env = zip_ty_env tvs tys (extendVarEnv env tv ty)
+ -- There used to be a special case for when
+ -- ty == TyVarTy tv
+ -- (a not-uncommon case) in which case the substitution was dropped.
+ -- But the type-tidier changes the print-name of a type variable without
+ -- changing the unique, and that led to a bug. Why? Pre-tidying, we had
+ -- a type {Foo t}, where Foo is a one-method class. So Foo is really a newtype.
+ -- And it happened that t was the type variable of the class. Post-tiding,
+ -- it got turned into {Foo t2}. The ext-core printer expanded this using
+ -- sourceTypeRep, but that said "Oh, t == t2" because they have the same unique,
+ -- and so generated a rep type mentioning t not t2.
+ --
+ -- Simplest fix is to nuke the "optimisation"
+
+instance Outputable TvSubst where
+ ppr (TvSubst ins env)
+ = sep[ ptext SLIT("<TvSubst"),
+ nest 2 (ptext SLIT("In scope:") <+> ppr ins),
+ nest 2 (ptext SLIT("Env:") <+> ppr env) ]
+\end{code}
+
+%************************************************************************
+%* *
+ Performing type substitutions
+%* *
+%************************************************************************
+
+\begin{code}
+substTyWith :: [TyVar] -> [Type] -> Type -> Type
+substTyWith tvs tys = substTy (zipTvSubst tvs tys)
+
+substTy :: TvSubst -> Type -> Type
+substTy subst ty | isEmptyTvSubst subst = ty
+ | otherwise = subst_ty subst ty
+
+substTys :: TvSubst -> [Type] -> [Type]
+substTys subst tys | isEmptyTvSubst subst = tys
+ | otherwise = map (subst_ty subst) tys
+
+deShadowTy :: Type -> Type -- Remove any shadowing from the type
+deShadowTy ty = subst_ty emptyTvSubst ty
+
+substTheta :: TvSubst -> ThetaType -> ThetaType
+substTheta subst theta
+ | isEmptyTvSubst subst = theta
+ | otherwise = map (substPred subst) theta
+
+substPred :: TvSubst -> PredType -> PredType
+substPred subst (IParam n ty) = IParam n (subst_ty subst ty)
+substPred subst (ClassP clas tys) = ClassP clas (map (subst_ty subst) tys)
+
+-- Note that the in_scope set is poked only if we hit a forall
+-- so it may often never be fully computed
+subst_ty subst@(TvSubst in_scope env) ty
+ = go ty
+ where
+ go ty@(TyVarTy tv) = case (lookupVarEnv env tv) of
+ Nothing -> ty
+ Just ty' -> ty' -- See Note [Apply Once]
+
+ go (TyConApp tc tys) = let args = map go tys
+ in args `seqList` TyConApp tc args
+
+ go (PredTy p) = PredTy $! (substPred subst p)
+
+ go (NoteTy (SynNote ty1) ty2) = NoteTy (SynNote $! (go ty1)) $! (go ty2)
+ go (NoteTy (FTVNote _) ty2) = go ty2 -- Discard the free tyvar note
+
+ go (FunTy arg res) = (FunTy $! (go arg)) $! (go res)
+ go (AppTy fun arg) = mkAppTy (go fun) $! (go arg)
+ -- The mkAppTy smart constructor is important
+ -- we might be replacing (a Int), represented with App
+ -- by [Int], represented with TyConApp
+ go (ForAllTy tv ty) = case substTyVar subst tv of
+ (subst', tv') -> ForAllTy tv' $! (subst_ty subst' ty)
+
+substTyVar :: TvSubst -> TyVar -> (TvSubst, TyVar)
+substTyVar subst@(TvSubst in_scope env) old_var
+ | old_var == new_var -- No need to clone
+ -- But we *must* zap any current substitution for the variable.
+ -- For example:
+ -- (\x.e) with id_subst = [x |-> e']
+ -- Here we must simply zap the substitution for x
+ --
+ -- The new_id isn't cloned, but it may have a different type
+ -- etc, so we must return it, not the old id
+ = (TvSubst (in_scope `extendInScopeSet` new_var) (delVarEnv env old_var),
+ new_var)
+
+ | otherwise -- The new binder is in scope so
+ -- we'd better rename it away from the in-scope variables
+ -- Extending the substitution to do this renaming also
+ -- has the (correct) effect of discarding any existing
+ -- substitution for that variable
+ = (TvSubst (in_scope `extendInScopeSet` new_var) (extendVarEnv env old_var (TyVarTy new_var)),
+ new_var)
+ where
+ new_var = uniqAway in_scope old_var
+ -- The uniqAway part makes sure the new variable is not already in scope
+\end{code}
+
+